Nested Select case in QBASIC

 

Nested Select case in QBASIC

In QBASIC, you can use the SELECT CASE statement to perform different actions based on the value of an expression. You can nest SELECT CASE statements by placing one SELECT CASE block inside another. Here is an example of how you can use nested SELECT CASE statements in QBASIC.

Syntax:

SELECT CASE expression1

    CASE value1

        SELECT CASE expression2

            CASE value2

                statements

            CASE value3

                statements

            CASE ELSE

                statements

        END SELECT

    CASE value4

        SELECT CASE expression3

            CASE value5

                statements

            CASE value6

                statements

            CASE ELSE

                statements

        END SELECT

    CASE ELSE

        statements

END SELECT

Note: Here, the inner SELECT CASE statement will be executed based on the value of expression2, and the outer SELECT CASE statement will be executed based on the value of expression1.

 

Example: 1

INPUT "Enter a number:", num

SELECT CASE num

    CASE 1

        PRINT "You entered 1."

    CASE 2

        SELECT CASE num

            CASE 2

                PRINT "You entered 2."

            CASE ELSE

                PRINT "You did not enter 1 or 2."

        END SELECT

    CASE 3

        SELECT CASE num

            CASE 3

                PRINT "You entered 3."

            CASE ELSE

                PRINT "You did not enter 1, 2, or 3."

        END SELECT

    CASE ELSE

        PRINT "You did not enter a valid number."

END SELECT

In above  example, the outer SELECT CASE block evaluates the value of num. If num is equal to 1, the program prints "You entered 1." If num is equal to 2, the program enters the first inner SELECT CASE block. If num is equal to 3, the program enters the second inner SELECT CASE block. If num is not equal to any of the specified values, the program prints "You did not enter a valid number."

Output:

 

Example 2

DIM letter AS STRING

INPUT "Enter a letter:", letter

SELECT CASE letter

    CASE "A", "a"

        PRINT "You entered A."

    CASE "B", "b"

        SELECT CASE letter

            CASE "B", "b"

                PRINT "You entered B."

            CASE ELSE

                PRINT "You did not enter A or B."

        END SELECT

    CASE "C", "c"

        SELECT CASE letter

            CASE "C", "c"

                PRINT "You entered C."

            CASE ELSE

                PRINT "You did not enter A, B, or C."

        END SELECT

    CASE ELSE

        PRINT "You did not enter a valid letter."

END SELECT

In above example, the outer SELECT CASE block evaluates the value of letter. If letter is equal to "A", the program prints "You entered A." If letter is equal to "B", the program enters the first inner SELECT CASE block. If letter is equal to "C", the program enters the second inner SELECT CASE block. If letter is not equal to any of the specified values, the program prints "You did not enter a valid letter."

Output: